1. Field of the Disclosed Subject Matter
The present disclosed subject matter relates to an automatic injection device for injecting a substance, such as a therapeutic agent, into a patient.
2. Description of Related Art
One of the most common routes of administration for therapeutic agents, such as medications, is by injection, such as intravenous, subcutaneous or intramuscular injection. A syringe containing the medication is used for the injection, which typically is carried out by trained medical personnel. In certain instances, a patient is trained in the use of the syringe to allow for self-injection. Moreover, certain medications are formulated in pre-filled syringes for patient use, to avoid the need for the patient to fill the syringe. Some patients, however, can be averse to carrying out self-injection, particularly if the patient has a fear of needles or limited dexterity.
Automatic injection devices offer an alternative to a syringe for delivering a therapeutic agent. Automatic injection devices have been used, for example, to deliver medications under emergency conditions, such as to administer epinephrine to counteract the effects of a severe allergic reaction, for example, as caused by a food allergy. Automatic injection devices also have been described for use in administering antiarrhythmic medications and selective thrombolytic agents during a heart attack (see e.g., U.S. Pat. Nos. 3,910,260; 4,004,577; 4,689,042; 4,755,169 and 4,795,433). Various types of automatic injection devices also are described in, for example, U.S. Pat. Nos. 3,941,130; 4,261,358; 5,085,642; 5,092,843; 5,102,393; 5,267,963; 6,149,626; 6,270,479; and 6,371,939, each of which is incorporated by reference herein in its entirety.
In general, prior automatic injection devices, when operated, have a needle of a syringe configured to move forward and project from a protective housing prior to actuation of the piston of the syringe to eject a dose of liquid through the needle. Movement of the syringe toward the patient's skin such that the needle is exposed before pressurizing a liquid charge inside the syringe can help prevent the liquid from being discharged from the needle before the actual injection takes place.
However, there remains a need for further improvement of known automatic injection devices. For example, it can be desirable to inspect the contents of the automatic injection device prior to use. Also, it can be desirable to indicate when injection is completed. Such features are available in certain automatic injection devices, the features depend upon larger volume doses. However, there remains a need for an automatic injection device suitable for different volume doses and/or a wider range of dose volumes.